Nice young trichs! They're all looking good! Flushing isn't as important in organics as it is with chem nutes. Your right. Fox farms is pretty hot soil & you can't actually rid it of the organic nutes anyway. What you're doing is flushing out the disolved nutes that would be the most easily/rapidly absorbed by the root hairs. I don't like commercial flush products, because like you mentioned about 'striping' the roots, the chemical products do that in a big way. By doing away with the disolved nutes, your making the plant rely more on the stored energies for bud ripening. These stored nutes & energies don't taste good in your smoke. One of these products being chlorophyll. You want all this to slow down a week or two before harvest. The epsom salts doesn't assist the flush, what it does is insure the plant has adequate magnesium or you can't get the buds to burn. They become 'fire proof'. So if you flush one without the epsom, compare it to the one with epsom for burnability. If you've ever harvested a lb or two that won't burn (& I have), you'll be afraid to omit the epsom. Since I find I can't taste the epsom salts, I always use it with my flush. Molasses does have some magnesium, so your buds still may burn fine without the epsom, but after that experience in the 80's, I'm always leary. One of those 'better safe than sorry' things. Not sure on this, but I don't THINK big bloom has anything you can taste in the final product, so if you want to chance it, you could try a sm amount in your flush, or maybe the next watering after that @ 1/4 strength. By using only plain water therafter, shouldn't be anything left to taste.
-- But hey! The hard work is done & this is you relaxation time! So sit back & enjoy. Your need to save your energy for harvesting & bud trimming! Then if you've time & energy left, check out all the things you can do with the leaf, cannabutter, green dragon, RSO, etc (don't forget to check out recipes)! Waste not want not!